If teachers were ever in any doubt about their worth to the economy, assessment guru Dylan Wiliam has produced some statistics to justify their continued employment in times of recession.
"Raising achievement matters economically," he told a masterclass in formative assessment in North Lanarkshire, run in conjunction with the Tapestry Partnership.
By getting students to stay on at school until the age of 18, the United States estimates teachers create a $210,000 (pound;132,799) benefit per person by making savings for the criminal justice system, improving health outcomes and producing increased economic growth.
Worldwide, there has been a 14 per cent rise in demand for complex communication skills and an 8 per cent rise in demand for expert thinking and problem-solving. On the other hand, the demand for routine manual skills has fallen by 5 per cent in 20 years. The fastest drop in demand has been for routine cognitive skills - bad news for teachers, says Professor Wiliam, deputy director of the Institute of Education in London, because "we are good at teaching them".
He suggested that, although some routine manual jobs would remain, the UK was likely to see them decline from two million to 600,000, which would be less and less well-paid.
The co-author with Paul Black of one of the seminal books on formative assessment, Inside the Black Box, Professor Wiliam argues that the focus must be on improving learning and teaching in schools if the UK wants to produce better-skilled young people.
Curriculum reform on its own will not make a difference, he told the North Lanarkshire conference, but formative assessment as a vehicle for changing the curriculum would. He added that 93 per cent of the difference between schools had nothing to do with them, but with the difference in intake. Class sizes made very little difference, except in P1-2, and maybe in P3, and setting by ability did not confer any benefits.
"The big factor is the quality of the teacher," he said. "The unions north and south of the border have resisted the idea that teachers are variable in quality. They agree that there are some incompetent teachers and that they should be fired, but argue that the rest are all good."
English teachers were better than maths teachers because there was considerably more competition for a teacher-training place in English; to get a PGCE place in maths in London, all you needed was a maths degree and a pulse - "and some would argue that the second was optional", he added.
It would take too long to get rid of the weakest teachers, so we have to "love the one you are with", improve CPD and raise teacher quality.
Professor Wiliam is working with the Tapestry Partnership in nine local authorities in Scotland to embed formative assessment techniques through Teacher Learning Communities (TLC), which he argues is the most effective method of raising skills levels.